U.S. patent number 7,201,793 [Application Number 11/047,967] was granted by the patent office on 2007-04-10 for ink-jet ink and ink-jet recording method.
This patent grant is currently assigned to Konica Minolta Holdings, Inc.. Invention is credited to Teruyuki Fukuda, Hirotaka Iijima, Yasuhiko Kawashima, Kenichi Ohkubo.
United States Patent |
7,201,793 |
Iijima , et al. |
April 10, 2007 |
Ink-jet ink and ink-jet recording method
Abstract
An ink for ink-jet recording containing: a colorant; and a set
of solvent A and solvent B, provided that solvent B has a larger
vapor pressure than solvent A, wherein the set of solvent A and
solvent B has a maximum in viscosity by changing a mixing ratio of
solvent A to solvent B; and a content of solvent A in weight
(A.sub.(wt)) and a content of solvent B in weight (B.sub.(wt)) in
the ink satisfy the following relationship:
50.ltoreq.[A.sub.(wt)/(A.sub.(wt)+B.sub.(wt))].times.100.ltoreq.95.
Inventors: |
Iijima; Hirotaka (Hachioji,
JP), Kawashima; Yasuhiko (Iruma, JP),
Ohkubo; Kenichi (Hachioji, JP), Fukuda; Teruyuki
(Hachioji, JP) |
Assignee: |
Konica Minolta Holdings, Inc.
(Tokyo, JP)
|
Family
ID: |
34824185 |
Appl.
No.: |
11/047,967 |
Filed: |
January 31, 2005 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20050172854 A1 |
Aug 11, 2005 |
|
Foreign Application Priority Data
|
|
|
|
|
Feb 9, 2004 [JP] |
|
|
2004-031739 |
|
Current U.S.
Class: |
106/31.58;
106/31.86; 347/100 |
Current CPC
Class: |
C09D
11/32 (20130101); C09D 11/40 (20130101) |
Current International
Class: |
C09D
11/02 (20060101); G01D 11/00 (20060101) |
Field of
Search: |
;106/31.58,31.86
;347/100 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
09-176538 |
|
Jul 1987 |
|
JP |
|
10-272828 |
|
Oct 1998 |
|
JP |
|
10-316915 |
|
Dec 1998 |
|
JP |
|
11-172174 |
|
Jun 1999 |
|
JP |
|
2000-095983 |
|
Apr 2000 |
|
JP |
|
2000-239591 |
|
Sep 2000 |
|
JP |
|
Primary Examiner: Lorengo; J. A.
Assistant Examiner: Faison-Gee; Veronica
Attorney, Agent or Firm: Frishauf, Holtz, Goodman &
Chick, P.C.
Claims
What is claimed is:
1. An ink for ink-jet recording comprising: a colorant; and a set
of solvent A and solvent B, provided that solvent B is water and
has a larger vapor pressure than solvent A, wherein the set of
solvent A and solvent B has a maximum in viscosity by changing a
mixing ratio of solvent A to solvent B; and a weight of solvent A
(A.sub.(wt)) and a weight of solvent B (B.sub.(wt)) in the ink
satisfy the following relationship:
10.ltoreq.[B.sub.(wt)/(A.sub.(wt)+B.sub.(wt))].times.100.ltoreq.50.
2. The ink for ink-jet recording of claim 1, wherein solvent A has
a vapor pressure of not more than 133 Pa measured at 25.degree.
C.
3. The ink for ink-jet recording of claim 1, wherein the colorant
is a pigment.
4. A method for ink-jet recording comprising the step of: jetting
the ink of claim 1 from a plurality of nozzles of an ink-jet head
of an ink-jet printer onto a recording material, wherein each of
the nozzles has a diameter of not more than 30 .mu.m; and the
ink-jet head is a piezo type head.
5. A method for ink-jet recording comprising the step of: jetting
the ink of claim 1 from a plurality of nozzles of an ink-jet head
of an ink-jet printer onto a recording material, wherein each of
the nozzles has a diameter of not more than 30 .mu.m; and the
ink-jet head is a line head of a piezo type.
6. A method for ink-jet recording comprising the step of: jetting
the ink of claim 1 from a plurality of nozzles of an ink-jet head
of an ink-jet printer onto a recording material, wherein each of
the nozzles has a diameter of not more than 30 .mu.m; the ink-jet
head is a line head of a piezo type; and a recording speed is not
less than 20 ppm.
7. A method for ink-jet recording comprising the step of: jetting
the ink of claim 1 from a plurality of nozzles of an ink-jet head
of an ink-jet printer onto a recording material, wherein each of
the nozzles has a diameter of not more than 30 .mu.m; and the
recording material is a paper.
Description
FIELD OF THE INVENTION
The present invention relates to a novel ink-jet ink and an ink-jet
recording method using the same.
BACKGROUND OF THE INVENTION
In ink-jet recording, recording of images and text is performed by
ejecting minute ink droplets based on various action principles to
be deposited on recording materials such as paper. Ink-jet
recording exhibits advantages such as relatively high speed, low
noise, and easy realization of multicolor formation.
In recent years, since ink-jet recording enables simple and less
expensive formation of images, it has been applied to various
printing fields such as photography, various kinds of printing,
marking, and special printing such as color filters. Specifically,
by employing ink-jet recording apparatuses which eject minute ink
droplets and control them, ink-jet inks which result in an improved
range of color reproduction, durability, as well as ejection
adaptability, and specialized paper sheets of which ink
absorbability, color forming properties of colorants and surface
glossiness are markedly improved, it has become possible to result
in image quality comparable to conventional silver salt
photography. Improvement in image quality of the current ink-jet
recording systems have only been achieved by integration of ink-jet
recording apparatuses, ink-jet inks, and recording materials.
In ink-jet printers employed for ink-jet recording, since recording
is performed by depositing ink droplets from ink-jet heads on
recording materials, the printers exhibit advantages such as easer
downsizing of the recording device, capability of recording highly
detailed images at a relatively high rate, lower running cost, and
the ease of recording of color images.
Of late, in view of highly detailed image recording, the nozzle
orifice size of ink-jet heads has decreased. However, when the
nozzle orifice size decreases, ink clogging and decap at the nozzle
section tend to occur. "Decap" indicates a phenomenon of clogging
at the nozzles caused by evaporation of a solvent (such as water)
contained in the ink. In order to minimize these problems,
maintenance such as suction and wiping of the nozzle section is
more frequently performed, resulting in necessity of longer
maintenance time in addition to image printing time. Specifically,
at present, since higher printing rates are demanded, an increase
in time required for the above maintenance due to the decreased
nozzle orifice size has become a major problem.
On the other hand, ink-jet printers are known which employ a serial
printing system in which scanning is performed in such a manner
that the ink-jet head moves in the direction which crosses the
conveyances direction of recording materials and a line printing
system in which the ink-jet head is fixed perpendicular to the
conveyance direction of recording materials.
In ink-jet printers employing the above line printing system, fixed
type parallel recording heads are employed which are arranged at a
right angle to the conveying direction of recording materials, and
in that system, recording is performed employing only secondary
scanning while recording materials are conveyed in the conveying
direction. While ink is ejected from the ink-jet heads and over-all
one-line recording is continuously performed, paper is conveyed at
a specified rate, whereby images are formed on the entire area of
the recording material. This method makes it possible to easily
achieve a high rate of printing. On the other hand, however, since
ink heads are fixed, resulting in mechanism making it difficult to
perform maintenance. As a result, as noted above, demand is
increasing to reduce maintenance time, due to ink clogging and
decap in the nozzle section as, short as possible.
On the contrary, in ink-jet printers employing the serial printing
system (hereinafter occasionally referred to as the shuttle head
system), while intermittently conveying the recording material,
images are formed by moving ink-jet heads in the direction which
crosses at right angles to the conveying direction of recording
materials. In these serial system ink-jet printers, it is easy to
perform maintenance, but has been difficult to consistently prepare
highly detailed images. Further, since ink-jet heads are
mechanically driven back and forth, there are drawbacks for
enhancement of the printing rate.
Proposed as a method to minimize clogging due to ink and decap,
which hinder an increase in printing rate and formation of highly
detailed images is, for example, one in which formation of a
network and aggregates in ink is minimized by incorporating anion
oxides as a surface active agent in the ink (refer, for example, to
Patent Document 1). However, employed as ink solvents, proposed in
the above method, are those composed of water exhibiting a high
vapor pressure as a main component. Subsequently, problems are
inherent in which capability capable of minimizing decap is limited
due to an increase in viscosity of ink liquid caused by water
evaporation.
Further proposed is a method (refer, for example, to Patent
Document 2), which selects ink constituting materials in such a
manner that water, water-soluble organic solvents, and
water-soluble dyes are employed so that even though components such
as water, which have a relatively high vapor pressure, are
evaporated, the resultant ink is not solidified and the variation
ratio of viscosity of the ink liquid is within a factor of ten,
compared to the initial viscosity. However, in this method, it
becomes necessary to select dyes which are highly soluble in
solvents which did not evaporate. As a result, diffusion of dyes
after being printed on recording materials increases, resulting in
bleeding.
Further, disclosed is ink in which specified latex polymers,
3-hexyl-2,5-diol, and 1,2-octane-diol are simultaneously used
(refer, for example, to Patent Document 3). However, in this
method, since an excessive added amount of 2-octanediol results in
feathering, its amount is limited with in the range of 0.01 0.5
percent by weight. Due to that, currently, decap is not minimized
as desired. Further, in this method, water at a relatively high
vapor pressure is employed as a major solvent. As a result,
problems are inherent in which decap minimizing effects are limited
due to an increase in viscosity caused by water evaporation.
As noted above, currently, a method has not been discovered which
simultaneously achieves formation of highly detailed images, high
rate printing, and minimization of decap.
On the other hand, in ink-jet image recording systems which
necessitate specialized paper sheets, problems occur in which
recording materials are limited and the cost of recording materials
increases. Specifically in offices, a system is increasingly
demanded which is capable of performing full-color printing at a
high rate without any limitation to recording materials (e.g.,
plain paper, coated paper, art paper, or double sided printing on
plain paper).
Various studies have been conducted with regard to compositions of
ink-jet inks capable of achieving higher speed printing, desired
text reproduction on plain paper, resulting in no ink penetration
to the back surface during printing (being the phenomena in which
printed ink passes through the recording material and a printed
image appears on the rear surface), no feathering, and no image
bleeding, as well as resulting in quick penetration into the
recording paper and rapid drying of the image.
As one of these methods, so-called water-based ink-jet inks are
widely employed. When images are recorded on plain paper such as
copy paper for electrophotography, high quality paper or medium
quality paper, in addition to problems such as image penetration to
the rear surface and feathering due to penetration, curling and
cockling of images recorded on plain paper result in major
problems.
In order to overcome the above drawbacks, an ink-jet recording
method is disclosed (refer, for example, to Patent Document 4)
which employs a penetration-improved ink by specifying the wetting
time and the absorption coefficient of recording materials in the
Bristow method. However, since colorants in the ink simultaneously
penetrate into plain paper, this method results in problems, in
which a decrease in image density as well as penetration to the
rear surface is enhanced, resulting in unsuitability for both sided
printing.
Further, ink-jet ink is disclosed (refer, for example, to Patent
Document 5) which incorporates specified amide compounds, pyridine
derivatives, imidazoline compounds or urea compounds as an anticurl
agent. However, this method results in problems in which clogging
of the nozzle of a recording head tend to occur due to drying of
liquid ink.
Still further, proposed is an ink-jet recording method to minimize
the above curling (refer, for example, to Patent Document 6), in
which curling balance is optimized by providing a solution
containing water on the side opposite the image printing surface.
However, this method results in problems in which along with an
increase in the adhered amount of ink as well as curl balance
liquid onto plain paper, its strength is deteriorated, whereby
jamming tends to occur during conveyance.
Still further, instead of using the water-based ink-jet ink, a
solvent-based ink capable of achieving printing at a high rate has
been studied. Namely, by employing an oil-based ink (being a
solvent-based ink-jet ink), even though printed on plain paper, it
is possible to achieve high speed printing due to quick penetration
into recording materials, shorter drying time, and no curling of
recording materials. However, problems occur in which text is not
reproduced as desired and penetration to the rear surface results
due to the fact that the solvent based ink easily penetrates plain
paper. (Patent Document 1) Japanese Patent Publication Open to
Public Inspection (hereinafter referred to as JP-A) No. 11-172174
(Patent Document 2) JP-A No. 2000-95983 (Patent Document 3) JP-A
No. 2000-239591 (Patent Document 4) JP-A No. 10-316915 (Patent
Document 5) JP-A No. 9-176538 (Patent Document 6) JP-A No.
10-272828
SUMMARY OF THE INVENTION
In view of the foregoing problems, the present invention was
achieved. An object of the present invention is to provide an ink
which exhibits excellent ejection stability in an ink-jet printer,
excellent decap durability, excellent text quality of formed
images, reduced rear surface penetration, and reduced curling
characteristic of printed recording materials, and an ink-jet
recording method using the same.
The aforesaid object of the present invention is achieved employing
an ink for ink-jet recording containing: a colorant; and a set of
solvent A and solvent B, provided that solvent B has a larger vapor
pressure than solvent A, wherein the set of solvent A and solvent B
has a maximum in viscosity by changing a mixing ratio of solvent A
to solvent B; and a weight of solvent A(A.sub.(wt)) and a weight of
solvent B(B.sub.(wt)) in the ink satisfy the predetermined
relationship which will be detailed below.
According to the present invention, it is possible to provide an
ink-jet ink which exhibits excellent ejection stability in an
ink-jet printer, excellent decap durability, excellent text quality
of formed images, reduced rear surface penetration resistance, and
reduced curling characteristic of printed recording materials, and
an ink-jet recording method using the same.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic diagram showing the change of viscosity in
accordance with the change of the ratio of solvent A to solvent
B.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of the present invention have the
following structures. (1) An ink for ink-jet recording
containing:
a colorant; and
a set of solvent A and solvent B, provided that solvent B has a
larger vapor pressure than solvent A,
wherein the set of solvent A and solvent B has a maximum in
viscosity by changing a mixing ratio of solvent A to solvent B; and
a weight of solvent A(A.sub.(wt)) and a weight of solvent
B(B.sub.(wt)) in the ink satisfy the following relationship:
50.ltoreq.[A.sub.(wt)/(A.sub.(wt)+B.sub.(wt))].times.100.ltoreq.95.
(2) The ink for ink-jet recording of the above-mentioned item
1,
wherein solvent B is water. (3) The ink for ink-jet recording of
the above-mentioned item 1 or item 2,
wherein solvent A has a vapor pressure of not more than 133 Pa
measured at 25.degree. C. (4) The ink for ink-jet recording of any
one of the above-mentioned items 1 to 3,
wherein the weight of solvent A (A.sub.(wt)) and the weight of
solvent B(B.sub.(wt)) in the ink satisfy the following
relationship:
10.ltoreq.[B.sub.(wt)/(A.sub.(wt)+B.sub.(wt))].times.100.ltoreq.50.
(5) The ink for ink-jet recording of any one of the above-mentioned
items 1 to 4,
wherein the colorant is a pigment. (6) A method for ink-jet
recording comprising the step of:
jetting the ink of any one of the above-mentioned claims 1 to 5
from a plurality of nozzles of an ink-jet head of an ink-jet
printer onto a recording material,
wherein each of the nozzles has a diameter of not more than 30
.mu.m; and the ink-jet head is a piezo type head. (7) A method for
ink-jet recording comprising the step of:
jetting the ink of any one of the above-mentioned claims 1 to 5
from a plurality of nozzles of an ink-jet head of an ink-jet
printer onto a recording material,
wherein each of the nozzles has a diameter of not more than 30
.mu.m; and the ink-jet head is a line head of a piezo type. (8) A
method for ink-jet recording comprising the step of:
jetting the ink of any one of the above-mentioned claims 1 to 5
from a plurality of nozzles of an ink-jet head of an ink-jet
printer onto a recording material,
wherein each of the nozzles has a diameter of not more than 30
.mu.m; the ink-jet head is a line head of a piezo type; and a
recording speed is not less than 20 ppm. (9) A method for ink-jet
recording of any one of the above-mentioned items 6 to 8,
wherein the recording material is a paper.
The present invention will be further detailed below.
When solvents are mixed to constitute a solvent set, by forming an
ink-jet ink containing a solvent set consisting of Solvent A which
exhibits the maximum point of the viscosity depending on the
resultant mixing ratio, and Solvent B which exhibits a larger vapor
pressure than the aforesaid Solvent A, and thereby a solvent set is
constituted to be in the region where the ratio of Solvent A is
higher than the aforesaid maximum section, and the content ratio
{[Solvent A/(Solvent B+Solvent A).times.100]} of aforesaid Solvent
A is 50 95 percent by weight.
It was discovered that it was possible to realize an ink-jet ink
which exhibited excellent ejection stability in an ink-jet printer,
for example, minimized lack of nozzles and deviated ejection of ink
droplets, exhibits excellent decap resistance, excellent text
quality on recording materials, reduced rear surface penetration,
and reduced curling characteristic due to liquid ink on the printed
recording material, whereby the present invention was achieved.
The maximum value of viscosity in the solvent set, as described in
the present invention, will now be described. Initially determined
is the viscosity of each of the solutions prepared by mixing
Solvent A with Solvent B in an optional ratio at an extreme of 100
percent Solvent A or 100 percept Solvent B. Subsequently, as shown
in FIG. 1, a graph, which shows the relationship of the viscosity
versus the solvent ratio in a solvent mixture, is prepared by
plotting the solvent ratio as the abscissa and the resulting
viscosity as the ordinate. In most cases, the viscosity versus the
solvent ratio monotonously increases or decreases as the ratio
varies. As shown by 1 in FIG. 1, combinations of solvents of the
present invention are specific and are characterized in that the
above relationship results in a maximum point.
The ink-jet ink of the present invention is constituted in the
region in which the content ratio of Solvent A is greater than the
ratio in-which the mixing ratio MA (in percent) of Solvent A and MB
(in percent) of Solvent B results in maximum value M in FIG. 1.
Further, it is characterized that the ratio of Solvent A is 50 95
percent by weight (the ratio range shown by region G in FIG.
1).
Further, it is characterized that the relationship of vapor
pressure of Solvent A and Solvent B is Solvent A>Solvent B.
Decap of ink jet heads is assumed as phenomena in which during
idling, viscosity increases due to evaporation of component
solvents in the ink, whereby the ejection rate of ink droplets
decreases or no ejection occurs.
In the present invention, by achieving the solvent constitution, as
described above, as Solvent B of a higher vapor pressure evaporates
(arrow a), the viscosity of the solvent mixture decreases (arrow
b). Based on this effect, since it is possible to minimize or
eliminate an increase in ink viscosity due to evaporation, it is
possible to retard the generation of decap. In more detail, as some
of ink evaporates, viscosity tends to increase due to an increase
in concentration of solutes. However, in the solvent constitution
of the present invention, a decrease in viscosity of solvents
minimizes the resulting viscosity variation, whereby it is possible
to minimize or eliminate an increase in viscosity (including a
decrease in viscosity).
Further, specifically, when printing is performed on highly
absorptive recording materials such as plain paper, ink does not
penetrate up to the rear surface, realizing in desired rear
penetration resistance. At the same time, it is possible to realize
image formation in such a manner that curling characteristic of
recording materials, on which images are formed, is not adversely
affected.
In the ink of the present invention, a solvent set is used which is
composed of at least Solvent A and Solvent B, provided that Solvent
B has a larger vapor pressure than Solvent A.
Solvent A, according to the present invention, is not particularly
limited as long as the vapor pressure is less than Solvent B, which
is employed in combination with Solvent A. The vapor pressure of
solvents is preferably at most 133 Pa at 25.degree. C., and is more
preferably 0.01 67 Pa. Further, as physical liquid properties of
Solvent A, its surface tension is preferably 25 40 mN/m at
25.degree. C., but is more preferably 25 32 mN/m. Further, the
viscosity of Solvent A is preferably 1 50 mPas, but is more
preferably 1 30 mPas.
Specific examples of Solvent A, according to the present invention,
include ethylene glycol monoalkyl ethers (e.g., ethylene glycol
monomethyl ether, ethylene glycol monoethyl ether, and ethylene
glycol monobutyl ether); diethylene glycol monoalkyl ethers (e.g.,
diethylene glycol monomethyl ether, diethylene glycol monoethyl
ether, and diethylene glycol monobutyl ether; triethylene glycol
monoalkyl ethers (e.g., triethylene glycol monomethyl ether,
triethylene glycol monoethyl ether, and triethylene glycol
monobutyl ether); propylene glycol monoalkyl ethers (e.g.,
propylene glycol monomethyl ether, propylene glycol monoethyl
ether, and propylene glycol monobutyl ether); dipropylene glycol
monoalkyl ethers (e.g., dipropylene glycol monomethyl ether,
dipropylene glycol monoethyl ether, and dipropylene glycol
monobutyl ether); tripropylene glycol monoalkyl ethers (e.g.,
tripropylene glycol monomethyl ether, tripropylene glycol monoethyl
ether; and tripropylene glycol monobutyl ether. Of these, preferred
are dialkylene glycol monoalkyl ethers or trialkylene glycol
monoalkyl ethers.
It is characterized that above Solvent A is incorporated in the
total of Solvents A with B commonly in an amount of 50 90 percent
by weight but preferably 60 90 percent by weight.
Solvents B are not particularly limited as long as their vapor
pressure is higher than that of Solvent A. Listed as Solvents B,
which are preferably usable in the ink of the present invention,
may, for example, be water, methanol, ethanol, 1-propanol,
2-propanol, and ethylene glycol. In view of more efficiently
exhibiting targeted effects of the present invention, water is
preferred.
In the ink of the present invention, the content ratio of Solvent B
is preferably 10 50 percent by weight with respect to the total
solvent with (Solvent A+Solvent B).
In the present invention, it is possible to obtain the viscosity as
well as the vapor pressure of each of the individual solvent and
mixtures thereof by referring to data of each described, for
example, in "Shinpan Solvent Pocket Book (New Edition Solvent
Pocket Book)" edited by Yuki Gosei Kagaku Kyokai, Omu Sha (1994),
or by employing prior art methods.
Other than each of the solvents according to the present invention,
various types of functional additives are incorporated in the ink
of the present invention.
The aforesaid solvents in the ink of the present invention contain,
if desired, colorants as well as various additives described below.
Preferably employed as colorants used in the present invention are,
for example, yellow, magenta, cyan, black, blue, green or red
colorants. Of these, yellow, magenta, cyan, and black colorants are
particularly favored.
It is possible to apply the ink of the present invention to various
types of ink-jet inks such as a dye ink which employs dyes as a
colorant, a pigment ink in which colorants are insoluble in the
solvents constituting the ink-jet ink, and a dispersion system
containing minute pigment particles is formed, or a dispersion ink
which is composed of a dispersion of polymers colored with
colorants.
Listed as dyes usable in the present invention may be azo dyes,
methine dyes, azomethine dyes, xanthene dyes, quinone dyes,
phthalocyanine dyes, triphenylmethane dyes, and diphenylmethane
dyes. Listed as specific compounds may, for example, be dyes
exemplified in JA-A No. 2002-264490.
Further, selected as oil-soluble dyes, which form minute colored
particles together with the aforesaid polymers to become colorants,
are dyes such as disperse dyes which are soluble in organic
solvents having no water-soluble group such as carboxylic acid or
sulfonic acid and which are insoluble in water. Further, included
are dyes which are prepared in such a manner that water-soluble
dyes are modified to become oil-soluble ones through formation of
salts with long chain bases. For example, known are dyes such as
acid dyes, direct dyes, or reactive dyes which form salts with long
chain amines.
However, in the ink of the present invention, it is preferred that
pigments are employed as a colorant. For resulting in sufficient
exhibition of the targeted effects, pigments which are insoluble in
the aforesaid solvent system are preferred.
Employed as pigments usable in the present invention may be those
known in the prior art without any limitation. It is possible to
use either water-dispersible dyes or oil-dispersible dyes. It is
also possible to preferably use, for example, organic pigments such
as insoluble pigments or lake pigments, as well as inorganic
pigments such as carbon black.
Examples of preferred insoluble pigments include, but not
particularly limited to, azo, azomethine, methine, diphenylmethane,
triphenylmethane, quinacridone, anthraquinone, perylene, indigo,
quinophthalone, isoindolinone, isoindoline, azine, oxazine,
thiazine, dioxazine, thiazole, phthalocyanine, and
diketopyrrolopyrrole.
Listed as specific pigments which are preferably usable are those
below.
Examples of pigments for magenta or red include: C.I. Pigment Red
2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I.
Pigment Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I.
Pigment Red 48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1,
C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139,
C.I. Pigment Red 144, C.I. Pigment Red 149, C.I. Pigment Red 166,
C.I. Pigment Red 177, C.I. Pigment Red 178, and C.I. Pigment Red
222.
Examples of pigments for orange or yellow are, include: C.I.
Pigment Orange 31, C.I. Pigment Orange 43, C.I. Pigment Yellow 12,
C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow
15, C.I. Pigment Yellow 17, C.I. Pigment Yellow 93, C.I. Pigment
Yellow 94, and C.I. Pigment Yellow 138.
Examples of pigments for green or cyan include: C.I. Pigment Blue
15, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment
Blue 16, C.I. Pigment Blue 60, and C.I. Pigment Green 7.
In addition to the above, when intermediate colors are required, it
is preferable that the following pigments are employed singly or in
combination. Examples of employed pigments include:
C.I. Pigment Red 177, 194, 209, and 224,
C.I. Pigment Orange 43
C.I. Vat Violet 3
C.I. Pigment Violet 19, 23, and 37
C.I. Pigment Green 7 and 36
C.I. Pigment Blue 15:6
Further examples of pigments for black are include: C.I. Pigment
Black 1, C.I. Pigment Black 6, and C.I. Pigment Black 7.
It is preferable that pigments employed in the present invention
are dispersed together with dispersing agents and necessary
additives to achieve various desired purposes, employing a
homogenizer and then employed, such as those known in the art,
including a ball mill, a sand mill, or a high pressure
homogenizer.
The average particle diameter in the pigment dispersion employed in
the ink of the present invention is preferably 10 200 nm, is more
preferably 10 100 nm, but is still more preferably 10 50 nm. When
the average particle diameter in the pigment dispersion exceeds 100
nm, the resulting dispersion becomes unstable, while when it is
less than 10 nm, stability of the pigment dispersion is degraded,
whereby storage stability of the ink tends to become
deteriorated.
It is possible to determine the particle diameter of a pigment
dispersion employing commercially available diameter measurement
devices using a light scattering method, an electrophoretic method,
or a laser Doppler method. Further, at least 100 particle images
are captured employing a transmission type electron microscope,
whereby it is possible to determine the particle diameter in such a
manner that the resulting images are subjected to statistical
processing employing image analysis software such as Image-Pro
(produced by Media Cybernetics).
In the ink-jet ink of the present invention, employed as additives
during dispersion may be surface active agents. Employed as surface
active agents usable in the present invention may be any of
cationic, anionic, amphoteric, or nonionic surface active
agents.
Listed as cationic surface active agents are aliphatic amine salts,
aliphatic quaternary ammonium salts, benzalconium salts,
benzetonium chloride, pyridinium salts, and imidazolinium
salts.
Listed as anionic surface active agents are fatty acid soap,
N-acyl-N-methylglycine salts, N-acyl-N-methyl-.beta.-alanine salts,
N-acylglutamic acid salts, acylated peptides, alkylsulfonic acid
salts, alkylbenzenesulfonic acid salts, alkylnaphthalenesulfonic
acids, dialkylsulfosuccinic acid ester salts, alkylsulfoacetic acid
salts, .alpha.-olefinsulfonic acid salts, N-acylmethyltaurine,
sulfonated oil, higher alcohol sulfuric acid ester salts, secondary
higher alcohol sulfuric acid ester salts, alkyl ether sulfuric acid
salts, secondary higher alcohol ethoxysulfates, polyoxyethylene
alkyl phenyl ether sulfuric acid salts, monoglysulfates, fatty acid
alkylolamide sulfuric acid ester salts, alkyl ether phosphoric acid
ester salts, and alkylphosphoric acid ester salts.
Listed as amphoteric surface active agents are carboxybetaine type,
sulfobetaine type, aminocarboxylic acid salts, and
imidazoliniumbetaine.
Listed as nonionic surface active agents are polyoxyethylene
secondary alcohol ether, polyoxyethylene alkyl phenyl ether,
polyoxyethylene sterol ether, polyoxyethylene lanolin derivatives,
polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene
glycerin fatty acid ester, polyoxyethylene sunflower flower oil,
hardened sunflower oil, polyoxyethylene sorbitol fatty acid ester,
polyethylene glycol fatty acid ester, fatty acid monoglyceride,
polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene
glycol fatty acid ester, sucrose fatty acid ester, fatty acid
alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene
alkylamine, alkylamine oxide, acetylene glycol, and acetylene
alcohol.
Further, in order to accelerate penetration of ink droplets after
ink ejection into plain paper, it is preferable to use surface
active agents. The above surface active agents are not limited as
long as they do not adversely affect storage stability of inks.
Employed as such surface active agents may be the same ones which
are used as an additive during the aforesaid dispersion.
Further, the total content of calcium ions, magnesium ions, and
iron ions, all of which are multivalent metal ions in the ink of
the present invention, is preferably at most 10 ppm, is more
preferably 0.1 5 ppm, but is most preferably 0.1 1 ppm.
By controlling the content of multivalent metal ions in an ink-jet
ink within the above specified range, it is possible to obtain inks
exhibiting high dispersion stability. Multivalent metal ions
related to the present invention are incorporated in the form of
sulfates, chlorides, nitrates, acetates, organic ammonium salts,
and EDTA salts.
In the ink of the present invention, in response to purposes to
enhance ejection stability, adaptability to printing heads and ink
cartridges, storage stability, and image retention properties, if
desired, other than those described above, it is possible to
appropriately select and employ various types of prior art
additives such as polysaccharides, viscosity modifiers, specific
resistance controlling agent, film forming agents, UV absorbers,
antioxidants, anti-discoloring agents, antiseptic agents, or
anti-rusting agents. Examples include minute oil droplets of liquid
paraffin, dioctyl phthalate, tricresyl phosphate, or silicone oil,
UV absorbers described in JP-A Nos. 57-74193, 57-87988, and
62-261476, anti-discoloring agents described in JP-A Nos. 57-74192,
57-87989, 60-72785, 61-146591, 1-95001, and 3-13376, as well as
optical brightening agents described in JP-A Nos. 59-42993,
59-52689, 62-280069, 61-242871, and 4-219266.
The surface tension of the ink of the present invention, which is
constituted, as above, is preferably 25 40 mN/m at 25.degree. C.,
is more preferably 25 35 mN/cm, but is still more preferably 30 35
mN/cm. Further, ink viscosity is preferably 1 40 mPas, at
25.degree. C., is more preferably 5 40 mPas, but is still more
preferably 5 15 mPas. Still further, oxygen concentration dissolved
in the ink of the present invention is preferably a maximum of 2
ppm at 25.degree. C. By satisfying the above conditions for the
dissolved oxygen concentration, it is possible to minimize
formation of air bubbles, whereby it is possible to realize an
ink-jet recording method which results in excellent ejection
stability even during high speed printing. It is possible to
determine the amount of oxygen dissolved in the ink employing, for
example, a dissolved oxygen measurement apparatus DO-14P (produced
by DKK-TOA Corp.).
In the image forming method employing the ink-jet ink of the
present invention, ink-jet prints are obtained in such a manner
that ink droplets are ejected from the ink-jet heads based on
digital signals, employing an ink-jet printer loaded with ink-jet
ink.
During image formation by ejecting the ink of the present
invention, employed ink-jet heads may use either an on-demand
system or a continuous system. Further, employed as an ejection
system may be any of the electric-mechanical conversion system
(e.g., a single-cavity type, a double-cavity type, a bender type, a
piston type, a share mode type, or a shared wall type), or an
electric-thermal conversion system (e.g., a thermal ink-jet
type,.or a Bubble Jet (registered trade name) type.
In these methods, the ink-jet recording method of the present
invention is characterized in that recording is performed on
recording materials by ejecting the ink of the present invention
from piezo type ink-jet recording heads at a maximum nozzle
diameter of 30 .mu.m, further, recording is performed on recording
materials by ejecting the ink of the present invention from piezo
type ink-jet recording heads at a nozzle diameter of at most 30
.mu.m of the line head system, or recording is performed on
recording materials employing piezo type ink-jet recording heads at
a maximum nozzle diameter of 30 .mu.m at a printing rate of 20
ppm.
By carrying out printing, employing recording heads of the line
head system as an ink-jet printer system instead of using the
recording heads of the shuttle head system, it is possible to fully
utilize the printing characteristics of the ink of the present
invention. As a result, it is possible to achieve the most desirous
dot shape (circularity) during the deposition of ink droplets on
recording materials, as well as desired printing accuracy.
Further, the ink of the present invention exhibits excellent
characteristics in terms of ejection stability and decap
resistance, as well as high rate printing. Subsequently, it is
preferable to achieve printing at a high rate of at least 20 ppm.
The printing rate is more preferably 20 100 ppm but is still more
preferably 25 50 ppm. The term "ppm", as described in the present
invention, refers to pages per minute, namely the number of printed
A4 size sheets, employed as a recording material, per minute.
Recording materials usable in the ink-jet recording method of the
present invention are not limited, as long as printing ink is
absorbed and held as desired. For example, it is possible to use
specialized ink-jet recording materials containing a non-absorptive
or absorptive support having thereon an ink absorptive layer which
absorbs and holds ink, as well as paper supports such as coated
paper or non-coated paper. However, in the ink-jet recording method
of the present invention, in view of resulting in desired rear
surface penetration resistant effects as well as resulting in high
quality text images, it is preferable to perform image printing
employing plain paper as the recording material.
Plain paper employed in the ink-jet recording method of the present
invention is not particularly limited, but non-coated paper,
special printing sheet paper, and 80 200 .mu.m thick non-coated
paper belonging to a part of information sheet paper are preferred.
Such plain paper according to the present invention is composed of
chemical pulp represented by LBKP and NBKP, sizing agents, and
fillers as major components, as well as, if desired, paper making
aids, and is made employing conventional methods. Simultaneously
employed as pulp materials used to make the plain paper according
to the present invention may be mechanical pulp and recycled waste
paper pulp. Further, these may be employed as main components
without any problem.
Listed as internally added sizing agents are, for example, rosin
size, AKD, al-nickel succinic anhydride, epichlorohydrin, cationic
starch, and acrylamide.
Further listed as fillers which are internally added to the plain
paper according to the present invention are, for example, minute
particle silicic acid powder, aluminum silicate, diatomaceous
earth, kaolin, kaolinite, halloysite, nacrite, dickite,
pyrophylite, sericite, titanium dioxide, and bentonite.
In view of minimizing the rear surface penetration of the ink of
the present invention, and enhancing fixability of colorants, the
pliant paper according to the present invention may incorporate
water-soluble multivalent metal salts.
The water-soluble multivalent metal salts usable in the plain paper
according to the present invention are not particularly limited.
For example, added are salts of metals such as aluminum, calcium,
magnesium, zinc, iron, strontium, barium, nickel, copper, scandium,
gallium, indium, titanium, zirconium, tin, or lead, as well as
salts such as sulfates, nitrates, formates, succinate, malonate,
chloroacetate, or toluenesulfonates. Further, employed as salts of
water-soluble multivalent metal ions may be water-soluble inorganic
polymers such as polychlorinated aluminum. In terms of solubility
in water, preferred are those which exhibit at least 0.1 percent by
weight and are more preferred which exhibit at least 1 percent by
weight. Of these, preferred are water-soluble salts composed of
aluminum, calcium, aluminum, magnesium, or zinc, because metal ions
of the resulting salts are colorless. Particularly preferred are
aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum
acetate, calcium chloride, calcium sulfate, calcium nitrate,
calcium acetate, magnesium sulfate, magnesium nitrate, magnesium
acetate, zinc chloride, zinc sulfite, zinc nitrate, and zinc
acetate.
EXAMPLES
The present invention will now be described with reference to
examples; however, the present invention is not limited
thereto.
<<Preparation of Inks>>
(Preparation of Pigment Inks 1 15)
Pigments, Solvent A, Solvent B (being water), and a pigment
dispersion were blended in the combinations listed in Table 1.
Thereafter, the resulting mixture was sealed in a glass bottle
together with 200 g of 1 mm diameter zirconia beads and was
dispersed over a period of two hours, employing a paint shaker,
whereby each of the pigment dispersions was prepared. Subsequently,
the zirconia beads were removed. Thereafter, the surface active
agent (added to some of the inks) and antiseptic agents, listed in
Table 1, were added to the resulting pigment dispersion and
vigorously mixed. Subsequently, the resulting liquid composition
was subjected to filtration and also to a membrane degassing
treatment employing a hollow fiber membrane, whereby Pigment Inks 1
15 were prepared.
(Preparation of Dye Inks 1 3)
In the combinations listed in Table 1, a dye Solvent A, Solvent B
(being water), and an antiseptic agent were blended and dissolved.
Thereafter, each of the resulting solutions was subjected to
filtration and a membrane degassing treatment, employing a hollow
fiber membrane, whereby Dye Inks 1 3 were prepared.
The numeric values listed in Table 1 refer to part by weight.
TABLE-US-00001 TABLE 1 Solvent B: Pigment Surface Solvent A Water
Colorant Dispersing Active Antiseptic Added Added Added Agent Agent
Agent Ink No. Type Amount Amount Type Amount *1 S104 Proxel Remarks
Pigment Ink 1 DPGmME 80 20 Pigment 1 5.0 2.0 -- 0.1 Inv. Pigment
Ink 2 DPGmME 80 20 Pigment 2 4.0 1.0 0.3 0.1 Inv. Pigment Ink 3
DPGmME 90 10 Pigment 1 5.0 2.0 -- 0.1 Inv. Pigment Ink 4 DPGmME 90
10 Pigment 1 5.0 2.0 0.3 0.1 Inv. Pigment Ink 5 TPGmME 90 10
Pigment 2 4.0 1.0 -- 0.1 Inv. Pigment Ink 6 TPGmME 85 15 Pigment 2
4.0 1.0 0.3 0.1 Inv. Pigment Ink 7 TPGmME 85 15 Pigment 2 4.0 1.0
-- 0.1 Inv. Pigment Ink 8 TEGmBE 90 10 Pigment 2 4.0 1.0 0.3 0.1
Inv. Pigment Ink 9 EG 80 20 Pigment 1 5.0 2.0 0.3 0.1 Comp. Pigment
Ink 10 TEG 70 30 Pigment 2 4.0 1.0 0.3 0.1 Comp. Pigment Ink 11
1,5-PDO 50 50 Pigment 1 5.0 2.0 0.3 0.1 Comp. Pigment Ink 12 DPGmME
40 60 Pigment 1 5.0 2.0 -- 0.1 Comp. Pigment Ink 13 TPGmME 40 60
Pigment 2 4.0 1.0 0.3 0.1 Comp. Pigment Ink 14 TPGmME 100 0 Pigment
1 5.0 2.0 0.3 0.1 Comp. Pigment Ink 15 EG 100 0 Pigment 1 5.0 2.0
0.3 0.1 Comp. Dye Ink 1 DPGmME 80 20 Dye 1 4.0 -- -- 0.1 Comp. Dye
Ink 2 TEG 70 30 Dye 1 4.0 -- 0.3 0.1 Comp. Dye Ink 3 TPGmME 40 60
Dye 1 4.0 -- -- 0.1 Comp. Inv.: Present Invention Comp.:
Comparative Example
Each of the additives, which are abbreviated in above Table 1, is
as follows:
<Solvent A>
EG: ethylene glycol TEG: triethylene glycol 1,5-PDO:
1,5-pentanediol DPGmME: dipropylene glycol monomethyl ether TPGmME:
tripropylene glycol monomethyl ether TEGmBE: triethylene glycol
monobutyl ether <Colorant: pigment> Pigment 1: C.I. Pigment
Red 122 Pigment 2: C.I. Pigment Blue 15:4 <Colorant: Dye> Dye
1: C.I. Solvent Blue 70 <Pigment Dispersing Agent> 1:
copolymer at a weight average molecular weight of 12,000, prepared
by copolymerizing methacrylic acid, methyl methacrylate,
2-ethylhexyl methacrylate, and hydroxythyl acrylate (at a weight
ratio of 40/20/10/30) <Surface Active Agent> S-104: Surfinol
104 (produced by Air Products Co.) <Antiseptic Agent> Proxel:
product of Avecia Limited (Characteristics of Solvent A, Solvent B
(water) employed for preparing each of the inks) (Vapor Pressure
and Viscosity of Individual Solvent) EG: viscosity of 16.8 mPas and
vapor pressure of 93 Pa TED: viscosity of 35.7 mPas and vapor
pressure of 23.1 kPa 1,5-PDO: viscosity of 93.5 mPas and vapor
pressure of less than 1 Pa DPGmME: viscosity of 3.1 mPas and vapor
pressure of 53 Pa TPGmME: viscosity of 5.3 mPas and vapor pressure
of 4 Pa TEGmBE: viscosity of 7.3 mPas and vapor pressure of 3 Pa
Water: viscosity of 0.87 mPas and vapor pressure of 3.16 Pa
Each of the above characteristic values is at 25.degree. C.
(Viscosity Characteristics of Mixed Solvent of Solvent A with
Water)
A solvent set was prepared in which the mixing ratio of Solvent A
to water was varied from 100:0 0:100 at intervals of 10 percent by
weight. Subsequently, the viscosity of each of the mixed solvents
was determined. Solvent Set of EG/water: In the course of varying
the mixing ratio, no maximum value of viscosity was noted, and the
viscosity of 100 percent EG was the maximum value (16.8 mPas).
Solvent Set of TEG/water: In the course of varying the mixing
ratio, no maximum value of viscosity was noted, and the viscosity
of 100 percent TEG was the maximum value (35.7 mPas). Solvent Set
of 1,5-PDO/water: Ion the course of varying the mixing ratio, no
maximum value of viscosity was noted, and the viscosity of 100
percent 1,5-PDO was the maximum value (93.5. mPas). Solvent Set of
DPGmME/water: Under a mixing condition at which DPGmME: water was
70:30, the maximum viscosity (of 6.4 mPas) resulted. Solvent Set of
TPGmME/water: Under a mixing condition at which TPGmME: water was
80:20, the maximum viscosity (of 10.1 mPas) resulted. Solvent Set
of TEGmBE/water: Under a mixing condition at which TEGmBE: water
was 80:20, the maximum viscosity (of 9.7 mPas) resulted.
Example 1
<<Ink-jet Image Recording>>
By employing a share mode piezo type recording head of a nozzle
aperture diameter of 32 .mu.m, a volume of ejected ink droplets of
20 pl, and 256 nozzles, as well as employing each of Pigment Inks
1, 3, 9, and 12 prepared as above, ejection was performed under
each of the conditions below, and decap resistance and intermittent
ejection adaptability were evaluated.
(Evaluation of Decap Resistance)
At an ambience of 23.degree. C. and 20 percent relative humidity, a
share mode piezo type recording head of 256 nozzles was employed,
and voltage applied to the recording head was controlled so that
the rate of ink droplets reached 8 m/second during an ejection
interval of 50 milliseconds as the initial state. Subsequently, the
ejection interval was varied and the relative ratio of the liquid
droplet rates was determined based on the formula below, whereby
decap resistance was evaluated based on the criteria below.
For example, 100 ink droplets were ejected at an ejection interval
of 50 microseconds, and 100 ink droplets were also ejected t second
after the initial ejection at an ejection interval of 50
microseconds. Subsequently, the rate of the initial ink droplet
after interval time t was determined and the resulting value was
designated as the ink droplet rate after interval time t.
The relative ratio of ink droplet rate (in percent)=(rate of ink
droplet after interval time t)/(rate of ink droplet at an ejection
interval of 50 milliseconds) A: interval time t was at least 10
seconds during which relative ratio of ink droplet rate became at
most 70 percent B: interval time t was 1 10 seconds during which
relative ratio of ink droplet rate became at most 70 percent C:
interval time t was 0.3 1 seconds during which relative ratio of
ink droplet rate became at most 70 percent D: interval time t was
less than 0.3 second during which Relative ratio of ink droplet
rate became at most 70 percent E: at 3-second intermittent
ejection, ink droplets were not ejected (Evaluation of Intermittent
Ejection Adaptability)
At an ambience of 23.degree. C. and 20 percent relative humidity,
each of Pigment Inks 1, 3, 9, and 12, prepared as above, was loaded
in a recording head and was allowed to stand for 8 hours.
Subsequently, under the same conditions, the ink was ejected. The
deposition state of ink droplets was observed, and intermittent
ejection adaptability was evaluated based on the criteria below. A:
after being allowed to stand, when ejection was conducted without
any treatment, all 256 nozzles achieved ejection B: after being
allowed to stand, when ejection was conducted without any
treatment, 1 5 nozzles resulted in deviated ejection, but ejection
returned to normal after one wiping operation of the recording head
C: after being allowed to stand, when ejection was conducted
without any treatment, 1 5 nozzles resulted in deviated ejection,
but ejection returned to normal by one suction and wiping operation
of the recording head D: after being allowed to stand, when
ejection was conducted without any treatment, at least 6 nozzles
resulted in deviated ejection, but ejection returned to normal by
two suction and wiping operations of the recording head E: After
being allowed to stand, when ejection was conducted without any
treatment, at least 6 nozzles resulted in deviated ejection, and
further it was not possible to return the ejection to normal even
after two suction and wiping operations of the recording head
Table 2 below shows these results.
TABLE-US-00002 TABLE 2 Intermittent Decap Ejection Ink No.
Resistance Adaptability Remarks Pigment Ink 1 A B Inv. Pigment Ink
3 A A Inv. Pigment Ink 9 C C Comp. Pigment Ink 12 D D Comp. Inv.:
Present Invention Comp.: Comparative Example
As can clearly be seen from the results in Table 2, the inks of the
present invention, containing the ink set which exhibited the
viscosity maximum at the mixing ratio specified by the present
invention and were composed of the specified mixing ratio,
exhibited excellent decap resistance as well as intermittent
ejection adaptability of the recording head, compared to the
comparative inks.
Example 2
Decap resistance and Intermittent Ejection Adaptability 1 were
evaluated in the same manner employing the methods described in
Example 1, except that Pigment Inks 2, 5, 6, and 10 were used, and
a share mode piezo type recording head of a nozzle aperture of 25
.mu.m, an ejected ink droplet volume of 4 pl, and 256 nozzles was
employed. Table 3 below shows these results.
TABLE-US-00003 TABLE 3 Intermittent Decap Ejection Ink No.
Resistance Adaptability Remarks Pigment Ink2 A B Inv. Pigment Ink5
A A Inv. Pigment Ink6 A A Inv. Pigment Ink 10 E E Comp. Pigment Ink
13 D E Comp. Inv.: Present Invention Comp.: Comparative Example
As can clearly be seen from the results of Table 3, even under
minute ink droplet conditions in which the diameter of the nozzle
aperture was 25 .mu.m and the ejected ink volume was 4 pl, the inks
of the present invention, which exhibited the viscosity maximum
portion depending on the mixing ratio specified by the present
invention and contained the ink set at the specified mixing ratio,
exhibited excellent decap resistance as well as excellent
Intermittent Ejection Adaptability 1, compared to the comparative
examples.
Example 3
An line head system ink-jet printer of a nozzle resolution per
color of 1,440 dpi (dpi, as described in the present invention,
represents the number of dots per 2.54 cm) and a total number of
2,560 nozzles was employed in which 10 share mode piezo type
recording heads (each at a nozzle aperture of 25 .mu.m, an ejected
ink volume of 4 pl, and 256 nozzles), described in Example 1, were
arranged in a line across the width direction. To the above ink-jet
printer, each of Pigment Ink 1, 3, 9, 12 was loaded, and driving
voltage was controlled to reach an 8 m/second ink droplet rate and
a 4 pl ink droplet volume.
Subsequently, employed, as a recording material, A4 plain business
class paper produced by Konica Minolta Corp., continuous printing
was performed at a rate of 10 ppm, while the short edge of the A
size paper was directed to the conveying direction. During the
above operation, the interval between sheets of plain paper was set
at 10 mm and the following images were printed, whereby Images 1 4
were produced.
Incidentally, the above printing rate (being the conveying rate of
plain paper) 100 ppm refers to the rate of printing 10 sheets of A4
size plain paper per minute, namely 2,200 mm/minute.
<<Evaluation of Intermittent Printing
Adaptability>>
At an ambience of 23.degree. C. and 30 percent relative humidity,
employing the above ink-jet printer, a 40 by 45 mm solid image was
continuously printed onto A4 size plain paper at a resolution, in
the major scanning direction, of 1,440 dpi. During this printing, a
pattern was repeated in which 283 ink droplets were continuously
ejected (for approximately 0.27 second), ejection was terminated
over a period of approximately 5.73 seconds, and subsequently 283
ink droplets were ejected. In such a manner, 50 sheets of plain
paper were continuously printed. Subsequently, the final 50th print
was visually observed, and intermittent printing adaptability was
evaluated based on the criteria below. A: no visual image mottling
was noted, and no lack in the outline portion was noted, resulting
in a good image B: very slight uneven density which did not result
in streaking was noted, but no generation of lack in the outline
portion was noted C: the outline of the image of the front portion
in the conveying direction was not aligned D: only one white streak
was noted E: two white streaks were generated <<Evaluation of
Character Quality>> Employing the above method, the following
Chinese characters were printed: and at a recording resolution of
1,440.times.1,440 dpi, employing in an MS Ming font of a size of
4-point, 5-point, and 6-point. The printed character images were
visually observed and character quality was evaluated based on the
criteria below. A: all 4-point characters were clearly recorded in
detail B: it was easy to read 4-point characters C: it was
difficult to read 4-point characters, but it was possible to read
5-point characters D: it was difficult to read 4-point and 5-point
characters, but it was possible to read 6-point characters E: it
was difficult to read 6-point characters <<Evaluation of
Reduced Curling Characteristic After Printing>>
At an ambience of 23.degree. C. and 30 percent relative humidity,
employing the above ink-jet printer, a 200.times.280 mm solid image
was printed onto A4 size plain paper at a resolution of
1,440.times.1,440 dpi. Subsequently, at an ambience of 23.degree.
C. and 20 percent relative humility, the printed plain paper was
allowed to stand on a flat stand over a period of one week so that
the printed surface faced up. Subsequently, the elevation of each
of the four corners was measured, and reduced curling
characteristic was evaluated based on the criteria below. A: almost
true flatness was noted and elevation of any of the corners was
less than 5 mm B: the largest elevation of any of the corners was 5
10 mm C: the largest elevation of any of the corners was 10 20 mm
D: the largest elevation of any of the corners was 20 50 mm E: the
largest elevation of any of the corners was at least 50 mm or it
was not possible to determine elevation due to formation of a
cylindrical roll
Table 4 shows these results.
TABLE-US-00004 TABLE 4 Intermittent Image Printing Character No.
Ink No. Adaptability Quality Curl Remarks 1 Pigment Ink 1 A B A
Inv. 2 Pigment Ink 3 A A A Inv. 3 Pigment Ink 9 D D E Comp. 4
Pigment Ink 12 E D C Comp. Inv.: Present Invention Comp.:
Comparative Example
As can clearly be seen from the results of Table 4, images, which
were formed employing the inks of the present invention, which
exhibited the viscosity maximum portion depending on the mixing
ratio specified by the present invention and contained the ink set
at the specified mixing ratio, exhibited excellent decap
resistance, excellent intermittent ejection adaptability, and
reduced curling characteristic, compared to the comparative
examples.
Example 4
<<Image Printing>>
Images 5 18 were prepared under the same image printing conditions
described in Example 3, except that the printing rate (the
conveying rate of plain paper) was changed to 200 ppm and each of
the inks described in Table 5 was employed.
<<Evaluation of Printed Images>>
Each of the images, prepared as above, was evaluated for
intermittent printing adaptability, text quality, and curling
characteristic based on the methods described in Example 3, as well
as ejection deviation and rear penetration after printing based on
the methods below. Table 5 shows these results.
(Evaluation of Line Deviation Resistance)
By employing the ink-jet printer described in Example 3, 50 checked
patterns (a width of one dot, and a length of 10.times.10 cm) were
printed on plain paper. The recorded checked line pattern was
visually observed and line deviation resistance was evaluated based
on the criteria below. A: neither line deviation nor line lack was
noted B: line deviation occurred at one position C: line deviation
occurred at two or three positions D: line deviation occurred at 4
10 positions or line lack occurred at one position E: line
deviation occurred at 11 or more positions or line lack occurred at
one or more positions (Evaluation of Transfer Resistance)
At an ambience of 23.degree. C. and 80 percent relative humidity,
by employing the above ink-jet printer, a 40 mm.times.40 mm solid
images were continuously printed at a resolution of 1,440
dpi.times.1,440 dpi on 100 A4 size sheets of plain paper. During
this printing, each sheet was stacked approximately 4 seconds
including the conveyance time after printing so that the surface of
printed sheet faced the rear surface of the subsequently printed
sheet, and the 100 sheets were stacked. Subsequently, each of the
image layer printing and the rear surface which had been stacked
were visually observed and transfer resistance was evaluated based
on the criteria below. A: no transfer from the image to the rear
surface was noted on 99 sheets B: slight transfer was noted in the
range of 1 10 sheets, but quality was commercially viable C: image
transfer was noted on the rear surface of almost all sheets,
resulting in problems for commercial viability
TABLE-US-00005 TABLE 5 Intermittent Line Image Printing Deviation
Character Transfer No. Ink No. Adaptability Resistance Curl Quality
Resistance Remarks 5 Pigment 2 A A A A A Inv. 6 Pigment 4 A A A A A
Inv. 7 Pigment 5 A A A A A Inv. 8 Pigment 6 A A A A A Inv. 9
Pigment 7 A A A A A Inv. 10 Pigment 8 A B C A B Inv. 11 Pigment 10
E D E B C Comp. 12 Pigment 11 E D E B C Comp. 13 Pigment 13 D D E C
C Comp. 14 Pigment 14 A A A D A Comp. 15 Pigment 15 A A E D C Comp.
16 Dye Ink 1 A A B B B Comp. 17 Dye Ink 2 E D E C C Comp. 18 Dye
Ink 3 D D C C C Comp. Inv.: Present Invention Comp.: Comparative
Example
As can clearly be seen from the results of Table 5, images, which
were formed employing the inks of the present invention, which
exhibited the viscosity maximum portion depending on the mixing
ratio specified by the present invention, and contained the ink set
at the specified mixing ratio, exhibited excellent intermittent
printing adaptability, and excellent character quality, reduced
curling characteristic, as well as, in addition, exhibited reduced
line deviation during injection and excellent transfer resistance,
compared to the comparative examples.
* * * * *